Scanning Tunneling Microscopy and Photons

Two different approaches to study the interaction of light with the electronic tunneling in a Scanning Tunneling Microscope (STM) will be discussed. If the surface of the semiconducting WSe2 is irradiated with visible light a surface photovoltage and a corresponding photocurrent can be observed. To investigate this effect the influence of light on the I‐V spectroscopy and the wavelength dependence of the photocurrent have been analyzed. The effect of the surface plasmons excited in a thin silver film on the tunneling process has been studied. The surface plasmons provide a very efficient coupling of the incoming light to the tunneling gap. The detection of the surface plasmons is due to the rectification of the optical ac‐field.